Forming machines, such as presses for massive forming or for sheet metal working, for example, for deep drawing or working of sheet metal parts in several stations, such as large-piece station presses, have tools with two tool halves which must work into one another at a relatively high precision. Although the moved tool half carries out relatively large strokes with respect to the tool size, and large forces act between the tool halves during the forming operation, the positioning of the tool halves with respect to one another has to take place in a precise manner. This applies particularly to tools with narrow function-defining gaps, as during cold extrusion, in the case of presses with several forming stations in one tool, as, for example, during massive forming, as well as in the case of large-piece station presses in which relatively thin-walled sheet metal parts are to be formed in a precise manner. Also in the case of punching machines, the precise positioning and guiding of upper dies with respect to a lower die may have increasing importance. This is particularly true when very narrow die clearances are desired.
From German Patent Document DE 3813235 C2, a special slide guidance for a fast-running punching machine is known, in the case of which the slide is constantly lubricated by correspondingly fed oil.
Increased precision demands cannot be met by lubrication alone.
Based on the above, it is an object of the invention to provide a forming machine which permits an improved working precision.
The forming machine according to the invention has at least a basic frame and a tool carried by the latter for forming workpieces. The workpiece tool) has, for example, a tool half carried by a slide and a tool half carried by the basic frame. For improving the working precision, particularly also during an operation of the forming machine for longer time periods, a cooling device is provided on the forming machine which is connected in a heat-transmitting manner at least with the basic frame or the tool. In this case, it may be sufficient for the cooling device to be connected only with one or a few parts of the basic frame and/or sections or parts of the tool in order to keep these cool and thus prevent a change of the dimensions as a result of temperature-caused extensions.
If the basic frame, for example, in the case of a large-piece station press is constructed of press stands and other parts, such as headpieces and bedplates, it may be sufficient to cool the press stands. As a result, the distance between the bedplate and the headpiece is maintained relatively precisely irrespective of the ambient temperature, whereby, in turn, during the closing of the tool, the gap existing between the two tool parts is maintained in a precise manner. Furthermore, it may be important to stabilize the dimension of a forming machine having several press stations in the passage or longitudinal direction in that carriers, which extend along several press stations, are each provided with at least one cooling duct and are therefore cooled. The bedplates and the headpieces can be included in the cooling as required. xe2x80x9cCoolingxe2x80x9d means that heat is dissipated from the corresponding parts irrespective of whether the temperature of the cooled part is above or below the ambient temperature.
The cooling, which can be provided as required, of a tool half, for example, of the lower tool, can be advantageous, for example, in the case of tools for massive forming. If the lower tool comprises several tool stations which are assigned, for example, to four successive forming stations, it can be prevented by means of the cooling that the lower tool heats up excessively during the running production and results in a change of the center distance of the individual tool stations. This permits a working with relatively narrow gaps between the upper tool and the lower tool and makes it possible to obtain particularly thin wall thicknesses during cold extrusion, an increased precision during massive forming and an improved endurance of the tools.
In every case, that is, when cooling the basic frame or its parts, as well as when cooling the tool or its parts, it is advantageous for the cooling device to be constructed as a thermostatic device. This means that the cooling performance is increased in the case of an increased heat output and an increasing temperature so that a defined limit temperature of the cooled parts is not exceeded. Here, it is particularly advantageous for the cooling device to be constructed as a latent-heat cooling system. This system contains a cooling medium which can absorb or deliver a larger amount of heat at a defined temperature, without changing its temperature in this case. The heat absorption can be connected with a phase transition (solid/liquid or liquid/gaseous). However, as an alternative and preferably, a cooling fluid is provided which is liquid above as well as below the defined latency temperature.
If its heat absorption capacity is sufficient, such a latent-heat cooling system permits maintaining the corresponding cooled areas of the tool or of the basic frame at a constant temperature. In particular, no temperature gradient occurs along the cooling duct by heating the coolant. Because of the uniform temperature, this permits an increased precision when guiding and positioning the movable tool part and the working of the tool part at a uniform temperature level. This allows the maintaining of narrow tolerances, which also applies to the cooling of a press frame by means of a latent-heat cooling system. In every case, it is expedient for the heat quantity to be absorbed by the latent-heat cooling medium on its path through the cooling duct to be lower than the latent heat quantity which can be absorbed. In addition, it is expedient to provide that, when entering into the cooling duct, the latent heat cooling medium already has the latent temperature but carries no latent heat or almost no latent heat yet. Thus, it is prevented that the beginning of the coolant duct becomes too cold.
The latent heat cooling medium can flow through the cooling duct and the cooling duct can also be constructed as a chamber with a resting latent heat cooling medium. In the latter case, one or several heat elimination ducts lead through the chamber filled with the latent head cooling medium or in its proximity in the thermal contact with the latter through the corresponding part. The latent heat cooling medium, whether it flows through a cooling duct or is situated in a corresponding chamber, is used for holding the corresponding tool or the corresponding part of the frame at a uniform temperature.
The carrying-away of heat from the cooling medium, particularly the latent heat cooling medium, preferably takes place by means of a heat exchanger. If the latent heat cooling medium is pumped through the cooling duct, it is circulated through the heat exchanger in order to supply its stored latency heat. As required, it can also be heated in the heat exchanger in order to bring the tool to the desired working temperature already at the start of the operation. This also applies to a basic frame or parts thereof.
For monitoring the latent heat cooling system, it is expedient to provide a heat capacity sensing device in the cooling duct and/or at its beginning and/or at its end which detects whether or not the latent heat cooling medium is capable of absorbing heat. The latent heat cooling medium forms a latent heat accumulator so that the corresponding parts of the forming machine which are penetrated by the cooling duct are connected with the thus formed latent heat accumulator. The charging and discharging of the latent heat accumulator will then be controlled by a control device which controls, for example, a coolant pump for circulating the latent heat accumulator medium. In the embodiment with the standing latent heat accumulator medium and the additional cooling duct, the circulation of the cooling medium in the additional cooling duct can be controlled. In addition, as required, the control device can act upon a heat exchanger or a device for carrying away heat connected here, in order to ensure the operation of the corresponding parts of the forming machine with latency temperature.
Detail of advantageous embodiments of the invention are contained in the drawing, the description or the subclaims. The drawing illustrates embodiments of the invention.